A multivariate climate index for the western coast of Colombia

Indices of the interannual and interdecadal variability at Tumaco Island (2° N; 79° W; Colombia), based on time series of sea surface temperature (SST), air temperature (AT) and precipitation (P) from a coastal station, are presented regarding the period 1960–2010. These indices are derived from the first two EOF (empirical orthogonal function) modes of the normalized time series, which grasp 84% of the explained variance. The first EOF represents the interannual variability closely correlated with the ENSO-related SST variability of region Ni o 1+2 (r = 0.74; lag = 1), Ni o 3 (r = 0.71; lag = 1), and the well-known period band 2–8 yr. Furthermore, the first EOF also accounts for the extreme warm events in the eastern equatorial Pacific due to them being well correlated with the E index (r = 0.70). The second EOF represents a much longer variability dominated by the ENSO-like mode or Pacific Decadal Oscillation (PDO), represented by two interdecadal modes (8–16 yr and 20–30 yr), and may account also with moderate warm events and cool events, being more sensitive to cool events.